Structure

If you have in mind a body of information to put across to your reader, you
probably have a mental organization for it. Normally this is a sort of
hierarchical tree, like the chapters of a book if you were to write a book.

Keep this structure. It helps readers to have a tree structure as a basis
for the book: it gives them a feeling of knowing where they are. You can
also use this structure for organizing your files in directories.